Preparation of water-dispersed formulation by nucleation and crystallization of low-melting point pesticide active ingredient

ABSTRACT

Agriculturally acceptable pesticidally active ingredients, such as herbicides, fungicides, and insecticides of low melting point, typically in the range from about 30° C. to about 130° C. and preferably in the range from about 30° C. to about 90° C. and low water solubility, typically in the range from about 0.01 ppm to about 1000 ppm and preferably in the range from about 0.01 ppm to about 300 ppm are frequently formulated as water-dispersed agrichemically acceptable formulations such as wettable powders (WP), water-dispersible granules (WG), and suspension concentrates (SC) and the like.

This application is a continuation of U.S. Ser. No. 08/785,250 filedJan. 17, 1997, now U.S. Pat. No. 5,688,743, which is a file wrappercontinuation of Ser. No. 08/223,334 filed Apr. 5, 1994, abandoned.

Agriculturally acceptable pesticidally active ingredients and mixturesthereof, such as herbicides, fungicides, and insecticides of low meltingpoint, typically having a melting point in the range from about 30° C.to about 130° C. and preferably in the range from about 30° C. to about90° C. (at normal atmospheric pressure) and low water solubility,typically in the range from about 0.01 ppm to about 1000 ppm andpreferably in the range from about 0.01 ppm to about 300 ppm areformulated using this invention as water-dispersed formulations such aswettable powders (WP), water-dispersible granules (WG), and suspensionconcentrates (SC). Nonlimiting examples of acceptable low melting pointpesticidal actives which can be used in this invention are found infamilies of pyridines, nitroanilines, acetanilides, organophosphates,triazines, pyrethroids, isoxazolidinones, carbamates, benzoxazoles,substituted phenoxys, substituted ureas, triazoles, oxadiazolinones,imidazolinones and azoryl chemistries, mixtures there of and the like.

Aging stability and suspensability (comparable to commercial formulationstandards) of WP, WG, and SC formulations requires a small dispersedparticle size (e.g. 2-20 μm mean size) containing the pesticidallyactive ingredient. Achieving this rather small particle size may requireformulation particle size reduction (e.g. grinding), by hammermill,media mill, air mill, and combinations thereof and the like.

Due to the rather low melting temperature of the pesticide activepreferably utilized in this invention, typically less than about 90° C.at normal atmospheric pressure, direct grinding (as in the art) of thediscrete solid pesticide active can be difficult due to melting orsoftening of the pesticide active itself during that grinding. Onepossible remedy, cryogenic grinding, is an option which may work, butwith added undesirable processing expense which makes it unattractiveand may not overcome resulting aging problems with the formulation.

Alternatively the pesticide active may be intentionally heated in asuitable container to a liquid melt physical state and then absorbedinto a relatively rigid, porous, powder carrier, such as precipitatedsilica or the like to provide improved grinding characteristics of thatcomposition versus grinding of the discrete solid pesticide active.These improved grinding characteristics assume that the once liquidactive has crystallized inside the porous powder carrier particles toallow such grinding.

If however the crystallization rate of the above described process istoo slow as happens using this absorption-grinding technique then thisabsorption method may not be practical. Without being bound by theory,it is believed that slow crystallization can be due to factors includinghigh viscosity in the supercooled liquid active, lack of seed surface toinitiate crystallization, low crystallization energy, etc. Supercooling,i.e. a cooling below the normal freezing point of a liquid withoutsolidification or crystallization occurring immediately, is a commontendency of many pesticide active ingredients.

Surprisingly, in the process of this invention, a quite different familyof nucleating agents was discovered to provide effective nucleation of asupercooled pesticide active (or a mixture of pesticide actives), andsubsequent rapid crystallization of the pesticide active, for practicalpreparation of WP, WG, SC, etc. formulation types from molten,low-melting point pesticide active ingredients. In carrying out theprocess of this invention, active ingredient crystallization is muchmore rapid, thorough, and predictable; otherwise, preparation of a waterdispersible formulation from a low melting pesticide active will be tooslow economically, or is likely to be poor quality.

OBJECTS OF THE INVENTION

It is an objective of the invention to provide an improved process inpreparing a water dispersible formulation from a low melting pesticideactive technical material.

Further, it is an objective of the invention to provide an enhancedprocess for preparing a dry, powder pesticidally active compositionwhich enables rapid crystallization of liquid technical in a carrier inthe composition.

It is yet another objective of this invention to provide a waterdispersible agriculturally acceptable composition which may be rapidlydispersed in water, which contains a low melt pesticide active.

These objects as well as other objects and advantages of the presentinvention will become apparent to those skilled in the art from thefollowing detailed description.

SUMMARY OF THE INVENTION

This invention comprises a practical method for preparing an enhancedagriculturally acceptable stable water dispersible formulation of alow-melting temperature active ingredient in which a compound selectedfrom the group consisting of carboxylic acids, esters, and amides,having melting point range of 30° C.-130° C. and having a chain lengthof about 3 to about 30 carbon atoms and preferably from about 5 carbonatoms to about 22 carbon atoms, is formulated to provide the enhancedinventive formulation which comprises the steps of:

a. admixing a low melt pesticide active(s) with a porous carrier, whichpreferably has been warmed to a temperature in the range from about 30°C. to about 130° C., preferably in the range from about 30° C. to about90° C. to form a dry intermediate powder wherein the pesticide activehas been absorbed as a liquid,

b. admixing with said dry intermediate powder, a nucleating agentselected from the above group to form a dry powder formulationintermediate,

c. cooling said dry powder formulation intermediate and admixingtherewith various functional ingredients to provide a dry or liquidformulation having commercial formulation characteristics, and

d. grinding said dry or liquid formulation to achieve desired dispersionparticle size whereby the formulation of this invention is prepared.

Granulation to make a dry formulation is an option.

Another embodiment comprises a practical method for preparing anenhanced agriculturally acceptable stable water dispersible formulationof a low-melting temperature active ingredient in which a compoundselected from the group consisting of carboxylic acids, esters, andamides, having melting point range of 30°-130° C. and having a chainlength of 5 to 22 carbon atoms, is formulated therewith to provide thisenhanced formulation which comprises the steps of:

a. admixing said nucleating agent selected from the above group with apesticide active to form a premix,

b. admixing said premix with a porous carrier which is at a temperaturein the range from about 30° C. to about 130° C., preferably from about30° C. to about 90° C. to form a dry, powder, formulation intermediatewherein the pesticide active has been absorbed as a liquid,

c. cooling said dry powder formulation intermediate and admixingtherewith various functional ingredients to provide for commercialformulation characteristics, and

d. grinding said formulation to achieve desired dispersion particle sizewhereby a dry or liquid formulation of this invention is prepared.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 Shows that molten dithiopyr technical did not crystallize uponcooling to -60° C.

FIG. 2 Shows that dithiopyr technical did not crystallize or melt uponwarming to 70° C.

FIG. 3. Shows that molten stearic acid crystallizes readily at about 60°C. upon cooling.

FIG. 4. Shows that crystalline stearic acid melted as expected at about65° C.

FIG. 5. Shows that the 4.3% stearic acid portion of a molten mixturewith dithiopyr crystallized at about 45° C. Crystallization of dithiopyrwas not apparent.

FIG. 6 Shows that when a mixture of supercooled dithiopyr andcrystalline stearic acid is heated, dithiopyr crystallized at about 25°C., followed by dithiopyr and stearic acid melting at about 56° C.

FIG. 7 Shows molten trifluralin partially crystallizing at about 0° C.

FIG. 8 Shows remainder of trifluralin crystallizing at about -12° C, andthen two crystal types melting at about 40° C. and about 47° C.

FIG. 9 Shows that the 4.8% stearic acid portion of a molten mixture withtrifluralin crystallized at about 43° C., followed by completecrystallization of trifluralin at about 17° C.

FIG. 10 Shows crystalline mixture of trifluralin and stearic acidmelting at about 40° C. and about 47° C., respectively.

FIG. 11 Shows that molten alachlor technical did not crystallize or meltupon cooling to -60° C. and then reheating.

FIG. 12 Shows that the 4.8% stearic acid portion of a molten mixturewith alachlor crystallized at about 29° C., and then a portion of thesupercooled alachlor crystallized at about -13° C.

FIG. 13 Shows that the sample with crystalline stearic acid, somecrystalline alachlor, and some supercooled alachlor, crystallizedfurther at about -32° C., and then fully melted at about 35° C.

FIG. 14 Shows that a dithiopyr sprayable formulation, based on stearicacid as nucleating agent, had greater efficacy on weeds than the ECsprayable formulation.

DETAILED DESCRIPTION OF THE INVENTION

This invention comprises a method for preparing an enhancedagriculturally stable acceptable water dispersible formulation of lowmelting temperature pesticide active (ingredient) in which a compoundselected from the group consisting of carboxylic acids, esters, andamides, having melting point range of 30° C.-130° C. and a chain lengthof about 3 to about 30 carbon atoms and preferably about 5 to about 22carbon atoms or mixtures thereof, are formulated to provide an enhancedwater dispersible formulation containing said pesticide active whichcomprises the steps of

a. admixing a low melt pesticide active with a porous carrier which hasbeen warmed to a temperature in the range from about 30° C. to about130° C., preferably from about 30° C. to about 90° C. to form a dryintermediate powder wherein the pesticide active has been absorbed as aliquid,

b. admixing with said dry intermediate powder, a nucleating agentselected from the above group to form a dry, powder formulationintermediate,

c. cooling said dry powder formulation intermediate and admixingtherewith various functional ingredients to provide a dry or liquidformulation having commercial formulation characteristics and thereafter

d. grinding said dry or liquid formulation to achieve desired dispersionparticle size whereby the formulation of this invention is prepared.

Using conventional granulation means thereafter to prepare a dryformulation is an option.

Another embodiment comprises a practical method for preparing anenhanced agriculturally stable acceptable water dispersible formulationof a low-melting temperature active ingredient in which a nucleatingagent selected from the group consisting of carboxylic acids, behenicacid methyl ester, and amides, having melting point range of 30°-130° C.and having a chain length of about 3 to 30 carbon atoms and preferablyabout 5 to about 22 carbon atoms or mixtures thereof, is formulatedtherewith to provide an enhanced dispersible agricultural formulationwhich comprises the steps of:

a. admixing said nucleating agent selected from the above group with apesticidal active to form a premix,

b. admixing said premix with a porous carrier which is at a temperaturein the range from about 30° C. to about 130° C., preferably from about30° C. to about 90° C. to form a dry, powder, formulation intermediatewherein the pesticide active has been absorbed as a liquid,

c. cooling said dry powder formulation intermediate and admixingtherewith various functional ingredients to provide for commercialformulation characteristics, and

d. grinding said formulation to achieve desired dispersion particle sizewhereby a dry or liquid formulation of this invention containing saidpesticide active is prepared.

Warming of the porous carrier to the desired temperature is preferablydone first.

Typical pesticide active ingredients of low melting point, and low watersolubility, which are frequently formulated as water-dispersedformulations such as wettable powders (WP), water-dispersible granules(WG), and suspension concentrates (SC) include acetanilides,nitroanilines, pyridines, organophosphates, triazines, pyrethroids,isoazolidinones, carbamates, benzoxazoles, substituted phenoxys,substituted ureas, triazoles, oxadiazolinones, imidazolinones, azorylsand more particularly include alachlor, trifluralin, dithiopyr,chlorpyrifos, ametryn, bifenthrin, clomazone, triallate,fenoxaprop-ethyl, diclofop-methyl, fenoxycarb, thiazopyr, oxyflurofen,linuron, imibenconazole, and oxadiazon. Mixtures thereof and the like ofpesticide actives may be employed in this invention.

The above pesticide actives are readily available, for example,alachlor, dithiopyr and triallate from Monsanto Company, trifluralinfrom Dow Elanco, chlorpyrifos from Dow Elanco, ametryn from Ciba-Geigy,bifenthrin and clomazone from FMC Corporation, fenoxaprop-ethyl anddiclofo-methyl from Hoechst-Roessel, fenoxycarb from Ciba Geigy,thiazopyr from Monsanto, oxyflurofen from Rohm and Haas, linuron fromDuPont, imibenconazole from Hokko Chemical Industry Co and oxadiazonfrom Rhone Poulenc.

Illustrative carboxylic acids useful in this invention include glutaricacid, myristic acid, stearic acid, mixtures thereof and of the like.Stearic acid is a preferred carboxylic acid.

A particularly useful amide is stearamide.

Various functional ingredients useful in this invention include water,alkyl sulfate salts, lignosulfonates, naphthalene sulfonates,polyvinylpyrrolidones, propylene glycol, biocides (e.g. Proxel), xanthangums, ethoxylated siloxanes or alkylphenols, quaternary alkyl ammoniumsalts, mixtures thereof and the like.

Mixtures of various carboxylic acids, esters and amides may be employedas nucleating agents in this invention.

The term "low melting point" as used herein means having a melting pointin the range from about 30° C. to about 130° C. and preferably fromabout 30° C. to about 90° C. although greater or less temperatures maybe used.

Suitable nonlimiting examples of carrier materials include inorganiccarrier materials precipitated silica or clay powder. Other suitablecarrier material which may be employed include, but are not limited toporous organopolymeric powders, such as polystyrene.

Inorganic or clay-type carriers useful herein can be obtained from theJ. M. Huber Corporation in Macon, Ga., such as Zeolex 7 or Hubersorb600, although other clays and mixtures may be utilized.

A useful precipitated silica may be obtained from PPG Industries,Pittsburgh, Pa. as HiSil ABS or from Degussa as Wessalon 50 althoughother substantially equivalent silicas and mixtures thereof may beutilized.

A useful stearic acid may be obtained from Witco Corporation in Memphis,Tenn. as Hystrene 9718 although other stearic acids and mixtures thereofmay be utilized.

Without being bound by theory it is believed that effective nucleationof the supercooled active, and subsequent rapid crystallization of theactive, are important in this invention for practical preparation of WP,WG, SC, etc. formulation types from molten, low-melting point activeingredients. Crystallization needs to be fairly rapid, thorough, andpredictable; otherwise, formulation preparation will be too sloweconomically, or of poor quality.

The term "stable" as used herein means meeting or exceeding theperformance under test of commercial standard formulations at ambientstorage temperature with respect to formulation homogeneity,dispersability and sprayability.

The term "commercial formulation characteristics", as used herein meansthat the formulation of this invention is commercially compatible withcurrent storage, handling and application practices of the intendeduser.

The term "rapid" as used herein means formation of a definite activeingredient crystal state in a time of less than about 5 hours andpreferably less than about 3 hours.

Illustratively crystallization begins when the nucleating agent iscrystalline and is in contact with supercooled, active ingredient.

Illustratively crystallization ends when the supercooled liquid activeingredient has become a crystalline solid.

The term "cooling" as used herein means cause or allow to cool so thatpesticide active crystallization may proceed.

In the process of this invention which is classified as an absorptionformulating method, the nucleating agent is chemically different fromthe active ingredient, i.e. crystallization is due to heterogeneousnucleation. In contrast, homogeneous nucleation is commonly practiced byaddition of solid active ingredient to a supercooled or super-saturatedliquid containing the same pesticide active. It is believed that thesolid pesticide active ingredient particles provide the surface (nuclei)for the liquid (containing the same active ingredient) to crystallizeon.! For the method herein, the class of nucleating agents arechemically quite different from actives for which faster crystallizationwas detected.

An absorption formulating method utilizes absorption of the liquidactive ingredient into a porous carrier as an essential step in qualityformulation preparation.

Without being bound by theory, the process of this invention workssurprisingly well by providing a seed surface for crystallization, andmay be generally called heterogeneous nucleation. The nucleating agentsare preferably chemically quite different from the active. Thenucleating agent can be either pre-mixed with a pesticide active(ingredient) prior to absorption into the porous carrier, or, if thenucleating agent melts at a convenient temperature, it can be absorbedas a separate molten ingredient. Once the absorption process isfinished, and a loaded powder intermediate composition of carrier andactive and nucleating agent is allowed to cool, the nucleating agentprovides a surface to enhance the crystallization rate of the nowsupercooled liquid active ingredient. Crystallization of this matriximproves grindability, and resistance to active ingredient migrationupon contact of the loaded powder with water. Low cost porous carriersare frequently hydrophilic; dispersion of the loaded powder in waterwith still-liquid active can result in displacement of the activeingredient from the carrier by water, a mode of formulation failure. Ofcourse, WP and WG formulations are dispersed in water during qualityanalysis, and by the end use customer. Also, dispersion of solids inwater occurs during the SC formulating. Therefore, the loaded powdermust be readily compatible with water contact.

In practicing the process of this invention, selection of compounds fornucleation of active ingredients is typically based on visual comparisonof crystallization rates for side-by-side samples and/or comparison ofDifferential Scanning Calorimetry (DSC) plots for active alone, versusactive and about 5 wt. % candidate nucleating agent. The utility ofthese two tests, for ranking candidate nucleating agent effectiveness,was initially determined by the later observed correlation with thissurprising sequence of observations with the pesticide active dithiopyr:

1. From the hot melt state, a dithiopyr bulk sample crystallized slowlyover about one day at 20° C. Sub-ambient cooling of the melt did notaccelerate crystallization possibly due to viscosity. This indicatedpotential difficulties in preparing a water-dispersible formulation fromdithiopyr melt since a major component of the formulation (dithiopyr)may remain liquid for greater than or about one day and could migrate,causing formulation failure.

2. A water-dispersible formulation precursor (loaded powder) wasprepared by mixing 49 wt % PPG Hisil T-700 precipitated silica with 51wt % dithiopyr technical melt at about 70° C. (Dithiopyr technical meltsat about 55° C.) Cooled the loaded powder to about 20° C. and let standfor about 2 hours and dispersed this loaded powder in water. Observedwhite silica solids and gold-colored particles of dithiopyr technicalformed immediately in the dispersion. This result showed that thedithiopyr was still liquid in the silica particles, was displaced bywater, and congealed in the aqueous phase.

3. Observation test #2 above was repeated, but by mixing 45% T-700, 52%technical and 3% stearic acid. Cooled the loaded powder to about 40° C,and immediately dispersed in water. Only white particles were seen, nogold-colored particles. This small proportion of stearic acid had animmediate effect; technical was not displaced upon mixing loaded powderwith water.

4. Observation test #2 above was repeated, but by mixing 88% T-700 and12% technical. Cooled the loaded powder to about 20° C. and held for 2days total. With periodic dispersion tests in water, gold-colorparticles of dithiopyr occurred each time. After 2 days storage,technical was still being displaced by water, and was apparently still asupercooled liquid in the silica particles, without stearic acid use.

As shown below in Examples 1 and 2, the following two methods, forevaluation of candidate nucleating agents, provided valuable insight andcorrelation with observations 1-4 above.

Crystallization Rate Visual Comparison

To one ounce flint glass B/R bottle from Fisher Scientific, add about11.5 grams liquid active ingredient and about 0.5 grams candidatenucleating agent. Place all capped bottles in oven to equilibratetemperature; active ingredient portion is liquid in all bottles;candidate agent may be liquid or solid depending on the selection.Bottles are placed at about 20° C. side-by-side for cool-down and visualobservations. Samples typically progress through the sequence: (1)flowable, (2) non-flowable and translucent, (3) non-flowable and opaque(which here defines the comparative crystallization time). Thenon-flowable and translucent state occurs when the candidate nucleatingagent is crystalline but the active ingredient is not, and as such isnot indicative of the active ingredient crystallization rate. Uponachieving the opaque state, all samples are ranked on a time-to-achievebasis.

Differential Scanning Calorimetry (DSC) Analysis

Prior to DSC analysis, samples are pre-heated to where the active isliquid. Sample is sealed in aluminum pan and held in DSC for 10 minutesabove the active melt temperature. The sample is cooled to -60° C. at-2° C./minute, and finally heated back to the original temperature at+2° C./minute. This procedure was established to generally follow thepractice of absorbing the active as a liquid into a porous carrier andthen cooling toward about 20° C. for crystallization. Criticalinformation from the DSC plots includes endotherm and exothermtemperature correlation and energy balance.

(Note--The same lot of an active ingredient is used throughout theExamples.)

EXAMPLE 1 Crystallization Rate Visual Comparison: Dithiopyr TechnicalMixtures

To each of twenty-two bottles was added 11.7±0.3 grams of dithiopyrtechnical (same lot) as a hot, liquid melt. Twenty-one potentialnucleating agents were added at 0.52±0.2 grams to these bottles asshown:

    ______________________________________                                        Bottle                    literature melting point                            #      Agent              ˜°C. for agent                         ______________________________________                                         1     glycerol monostearate flake                                                                      58                                                   2     sodium lauryl sulfate powder                                                                     205                                                  3     stearic acid flake 65                                                   4     polyethylene glycol 8000 powder                                                                  62                                                   5     none (dithiopyr technical only)                                                                  no agent                                             6     Witco Morwet EFW powder                                                                          no data                                              7     behenic acid, methyl ester powder                                                                54                                                   8     oleic acid liquid  13                                                   9     lauric acid powder 45                                                  10     dodecanedioic acid powder                                                                        129                                                 11     myristic acid flake                                                                              52                                                  12     palmitic acid flake                                                                              59                                                  13     behenic acid flake 69                                                  14     stearamide powder  103                                                 15     oleamide powder    73                                                  16     stearyl erucamide powder                                                                         74                                                  17     PPG Hisil ABS precipitated                                                                       no data                                                    silica powder                                                          18     glutaric acid powder                                                                             97                                                  19     phthalic acid powder                                                                             210                                                 20     malonic acid powder                                                                              136                                                 21     poly(acrylic acid) powder, ave.                                                                  no data                                                    molecular weight = 2000                                                22     poly(methyl methacrylate) powder,                                                                180                                                        average molecular weight                                               ______________________________________                                    

Bottles were capped and placed in oven at 75° C. until the physicalstate has stabilized (i.e. 100% liquid, or liquid technical+solidagent), taking 1-2 hours. Bottles were removed from oven and placedside-by-side at room temperature (˜23° C.). Changes of state aredetected by slight tipping of the bottles and visual inspection, versustime. Endpoint was defined as time to achieve 100% visually-opaquesolid. Results were:

    ______________________________________                                              Agent    time-                                                                state    to-                                                                  at       endpoint relative crystallization                                                                  Agent                                     Bottle #                                                                            startpoint                                                                             hours    rate, 1.0 = highest                                                                       Type                                      ______________________________________                                         1    liquid   ˜20                                                                              ˜0.03 C18 ester                                  2    solid    ˜20                                                                              ˜0.03 C12 sulfate                                3    liquid   2.5      0.30        C18 acid                                   4    liquid   ˜20                                                                              ˜0.03 polyether                                  5    no agent ˜20                                                                              ˜0.03 --                                         6    solid    ˜20                                                                              ˜0.03 anionic                                    7    liquid   2.0      0.38        C20-22 ester                               8    liquid   ˜20                                                                              ˜0.03 C18 ene acid                               9    liquid   ˜20                                                                              ˜0.03 C12 acid                                  10    solid    0.75     1.0         C12 diacid                                11    liquid   1.25     0.60        C14 acid                                  i2    liquid   4.0      0.19        C16 acid                                  13    liquid   5.0      0.15        C20-22 acid                               14    solid    1.5      0.50        C18 amide                                 15    liquid   7        0.11        C18 ene amide                             16    liquid   7        0.11        C18 ester                                 17    solid    ˜20                                                                              ˜0.03 silica                                    18    solid    1.5      0.5         C5 diacid                                 19    solid    ˜20                                                                              ˜0.03 aryl diacid                               20    solid    ˜20                                                                              ˜0.03 C3 diacid                                 21    solid    ˜20                                                                              ˜0.03 poly alkyl acid                           22    solid    ˜20                                                                              ˜0.03 poly alkyl ester                          ______________________________________                                    

This data identified C5 diacid, C12 diacid, C14 monoacid, C16 monoacid,C18 monoacid, C18 amide, C20-22 monoacid, and C20-22 ester as effectivenucleating agents, the dithiopyr portion crystallizing 17×, 30×, 20×,5×, 10×, 17×, 4×, and 13× faster than dithiopyr technical alone (Bottle#5), respectively. The remaining samples crystallized slightly tonegligibly faster than technical alone. The C14 acid, C18 acid, andC20-22 ester are preferred practical candidates for dithiopyr rapidcrystallization since these are also liquids near the dithiopyr melttemperature, allowing incorporation as liquids for more intimate contactwith dithiopyr technical. The crystallization sensitivity of dithiopyrto these eight compounds is surprising, considering that dithiopyr is achemically unrelated pyridine compound. As used herein, C18 means chainlength of 18 carbon atoms, Acid means carboxylic acid, and Ene meansalkene functionality.

This result was taken to imply that the lack of dithiopyr displacementby water from the loaded powder described above in the observationtests, was due to stearic acid causing dithiopyr to crystallize prior todispersing the loaded powder in water.

EXAMPLE 2 DSC Analysis: Dithiopyr Technical Mixtures

Since Example 1 identified stearic acid as enhancing technicalcrystallization rate by ten-fold, this difference should be detectableby DSC.

Three samples were run:

1. Sample Bottle #5, dithiopyr technical, above

2. stearic acid alone

3. Sample Bottle #3, ˜96% technical+˜4% stearic acid

Results:

1. Technical did not crystallize upon cooling from +70° C. to -60° C.Upon reheating, the most notable detail was a -25° C. glass transition(Tg). Since technical melting point is ˜55° C., supercooling isapparent. See FIG. 1 and FIG. 2.

2. Stearic acid exhibited predicted crystallizing and meltingtransitions at 60°-65° C. The energy values of 49-50 calories/gramclosely match literature values. No supercooling tendency seen. See FIG.3 and FIG. 4.

3. Cool-down scan integration suggested that stearic acid portion hascrystallized, but technical portion is supercooled. However, duringheat-up, the plot suggested that technical crystallizes at roomtemperature, and then both melt similar to a single component. Duringcool-down, apparently the viscosity of supercooled dithiopyr increasedtoo rapidly to allow dithiopyr crystallization. But, during heat-up,with time and less viscous technical, crystallization rapidly occurredin the presence of stearic acid crystals. See FIG. 5 and FIG. 6.

This data showed that stearic acid crystals will nucleate supercooleddithiopyr technical, causing dithiopyr crystallization.

EXAMPLE 3 Crystallization Rate Visual Comparison: Trifluralin TechnicalMixtures

To each of three glass bottles, added trifluralin technical. Potentialnucleating agents added to bottles were stearic acid, methyl behenate,and none (control), respectively. Place capped bottles in 75° C. for 2hours. Remove bottles, shake, and place side-by-side at about 23° C. forvisual observation. Crystallization endpoint reached in 1 hour, >67hours, and >67 hours, respectively.

Here, trifluralin technical was nucleated by a select compound from theabove group, stearic acid, causing trifluralin crystallization.

EXAMPLE 4 DSC Analysis: Trifluralin Technical Mixtures

Since Example 3 identified stearic acid as a nucleating agent forsupercooled trifluralin, DSC should detect differences.

Two samples were run:

1. trifluralin technical alone

2. trifluralin technical with 4.8% by weight stearic acid

Results:

1. Technical partially crystallized at ˜0° C. on cool-down, and finishedcrystallizing on heat-up at ˜0° C. See FIG. 7 and FIG. 8.

2. Stearic acid crystallized, followed by Technical completelycrystallizing at ˜17° C. on cool-down. See FIG. 9 and FIG. 10.

Here, stearic acid nucleated supercooled trifluralin technical, causingtrifluralin crystallization.

EXAMPLE 5 DSC Analysis: Alachlor Technical Mixtures

Two samples were run:

1. alachlor technical alone

2. alachlor technical with 5% stearic acid

Results:

1. During cool-down and heat-up, no melting or crystallization occurred.Technical remained supercooled. See FIG. 11.

2. Stearic acid crystallized on cool-down, followed by a portion of thealachlor crystallizing at ˜-15° C. On heat-up, more alachlorcrystallized, followed by melting of alachlor and stearic acid as onecomponent. See FIG. 12 and FIG. 13.

Here, alachlor technical was nucleated by a select compound from theabove group, stearic acid, causing alachlor crystallization.

Biological Activity

While evaluating the economic position of WP, WG, and SC formulations,one would compare the unit activity of formulations of this inventionagainst an organic solvent-based formulation, such as an emulsifiableconcentrate (EC). Some compositions of this invention have been used tokill or control weeds (pests) using standard testing proceduresemploying the application of a pesticidally effective amount of aformulation of this invention containing a pesticide active to a pest inan acceptable agronomic method. Observations of the effect of suchapplication over time showed the pesticidal effect as kill or control ofthe weed (pest).

A water-dispersible formulation of dithiopyr, utilizing stearic acid asnucleating agent, was compared to the commercial EC formulation inseveral field trials. See FIG. 14. As shown, the mean unit activity ofthe dispersible formulation in fact exceeded that of the EC. Thisdispersible formulation had the following approximate composition:

    ______________________________________                                                                Approximate                                                       Ingredient  weight %                                              ______________________________________                                        HiSil ABS     (Silica, precipitated)                                                                      36                                                              Dithiopyr Technical                                                                         40                                                Hystrene 9718 (stearic acid)                                                                              12                                                Stepanol ME Dry                                                                             (lauryl sulfate salt)                                                                        5                                                Darvan 404    (lignosulfonate salt)                                                                        5                                                Agrimer 30    (polyvinylpyrolidone)                                                                        2                                                ______________________________________                                    

It is to be understood that the present invention is not limited to thespecific embodiments shown and described herein, but may be carried outin other ways without departure from its spirit or scope. All parts areby weight herein unless otherwise specified.

What is claimed is:
 1. A method for preparing an enhanced agriculturallyacceptable stable water dispersible formulation of a low-meltingtemperature pesticide active in which a nucleating agent selected fromthe group consisting of carboxylic acids, esters, and amides or mixturesthereof, having a melting point range of about 30° to about 130° C. andhaving a chain length in the range from about 3 to about 30 carbon atomsand mixtures thereof, is formulated to provide an enhanced dispersibleagricultural formulation containing said pesticide active whichcomprises the steps of:a. admixing a low melt pesticide activeingredient with a porous carrier which has been warmed to a temperaturein the range from about 30° C. to about 130° C., preferably from about30° C. to about 90° C. to form a dry intermediate powder wherein thepesticide active has been absorbed as a liquid, b. admixing with saiddry intermediate powder with a nucleating agent selected from the abovegroup to form a dry, powder formulation intermediate, c. cooling saiddry powder formulation intermediate and admixing therewith variousfunctional ingredients as desired to provide a dry or liquid formulationhaving commercial formulation characteristics and thereafter d. grindingsaid dry or liquid formulation to achieve desired dispersion particlesize whereby a formulation of this invention is prepared.
 2. The processof claim 1 wherein said active ingredient is selected from the groupconsisting of pyridines, nitroanilines, acetanilides, organophosphates,triazines, pyrethroids, isoazolidinones, carbamates, benzoxazoles,substituted phenoxys, substituted ureas, triazoles, oxadiazolinones,imidazolinones, azoryls, mixtures thereof.
 3. The process of claim 2wherein said active ingredient is dithiopyr and said nucleating agenthas a chain length in the range from about 5 to about 22 carbon atoms.4. The process of claim 1 wherein said active ingredient is selectedfrom the group consisting of alachlor, chlorpyrifos, ametryn,bifenthrin, clomazone, triallate, fenoxaprop-ethyl, diclofop-methyl,fenoxycarb, thiazopyr, oxyflurofen, linuron, imibenconazole, oxadiazonand mixtures thereof.
 5. The process of claim 1 wherein said nucleatingagent is selected from the group consisting of stearic acid, glutaricacid, methyl behenate, and/or stearamide and mixtures thereof.
 6. Theprocess of claim 3 wherein said nucleating agent is stearic acid.
 7. Theprocess of claim 4 wherein said nucleating agent is stearic acid.
 8. Amethod for preparing an enhanced agriculturally stable acceptable waterdispersible formulation of a low-melting temperature pesticide activeingredient in which a nucleating agent selected from the groupconsisting of carboxylic acids, esters, and amides, having melting pointrange of 30°-130° C. and having a chain length of about 3 to about 30carbon atoms and mixtures thereof, is formulated which comprises thesteps of:a. admixing said nucleating agent selected from the above groupwith a pesticide active ingredient to form a premix, b. admixing saidpremix with a porous carrier which is at a temperature in the range fromabout 30° C. to about 130° C., preferably from about 30° C. to about 90°C. to form a dry, powder, formulation intermediate wherein the activeingredient has been absorbed as a liquid, c. cooling said dry powderformulation intermediate and admixing therewith various functionalingredients to provide for commercial formulation characteristics and d.grinding said formulation, which is optional for a dry formulation, toachieve desired dispersion particle size whereby a dry or liquidformulation of this invention containing said pesticide active isprepared.
 9. The process of claim 8 wherein said active ingredient isselected from the group consisting of pyridines, nitroanilides,acetanilides, organophosphates, triazines, pyrethroids, isoazolidinones,carbamates, benzoxazoles, substituted phenoxys, substituted ureas,triazoles, oxadiazolinones, and imidazolinones.
 10. The process of claim8 wherein said pesticide active ingredient is selected from the groupconsisting of dithiopyr, chlorpyrifos, ametryn, bifenthrin, clomazone,triallate, fenoxaprop-ethyl, diclofop-methyl, fenoxycarb, thiazopyr,oxyflurofen, linuron, imibenconazole, and oxadiazon.
 11. The process ofclaim 8 wherein said nucleating agent is stearic acid.
 12. The processof claim 9 wherein said nucleating agent is stearic acid.
 13. Theprocess of claim 9 wherein said nucleating agent is selected from thegroup consisting of stearic acid, glutaric acid, methyl behenate and/orstearamide.
 14. A pesticidally active composition prepared by theprocess of claims 1 to
 8. 15. A method of killing or controlling pestsby applying a pesticidally effective amount of a composition prepared bythe process of claims 1 to 8 to the pest or locus of the pest to bekilled or controlled.
 16. A pesticidal composition which comprises a lowmelt pesticide active ingredient, a nucleating agent selected from thegroup consisting of carboxylic acids, esters, and amides having amelting point in the range from about 30° to about 130° C. and having acarbon chain length in the range from about 3 to about 30, allfunctional ingredients as necessary to provide an acceptableformulation.